Forensic analysis is a scientific study which assists criminal investigations. Whenever any crime takes place there is exchange of material between the accused and the victim such as textile fibers, blood stains, gunshot residues, broken glass, saliva, semen, etc. Chemical and biological tests on such materials can provide undisputed evidence to nail down the suspect. However, forensic analysis poses a big challenge to the analyst. Firstly, the amount of sample collected from the scene of crime is often limited and it is just not possible to replenish it. Secondly, the results of such analysis can lead to conviction so findings need to be reported with extreme care so that innocent persons do not suffer. For this reason nondestructive techniques are preferred as the sample can subsequently be tested for further confirmation.

X-ray diffraction or XRD is one such technique which is nondestructive and the sample requires minimum sample preparation prior to analysis. The only requirement is that the sample should be homogeneous in nature so as to provide uniform analysis results even if a small portion is analysed from a bulk quantity. Samples commonly received for forensic testing commonly include:

Building materials such as cement, concrete, steel rods, bricks,etc

Drugs of abuse and other banned substances

Residues from site of arson such as kerosene oil, gasoline or cotton lints

The samples can be analysed by XRD if it exhibits a degree of crystallinity even if the remaining content is amorphous. The technique helps establish the presence or absence of a particular material through comparison against a reference XRD data base. The present article discusses some of the XRD applications of common samples picked up from scene of crime.

Drugs and pharmaceuticals

Drug and pharmaceutical samples are commonly seized from smugglers, carriers and from raids conducted on rave parties. Such substances can pose a challenge as their identity is seldom known. It can be a pure compound or even an engineered product produced by illegal laboratories to conceal their real identity. XRD helps identify one seized material from another or to identify the seized powder with known materials such as cocaine, morphine, heroin and amphetamines or different compounds introduced to conceal the real identity. Other analytical techniques such as visible light is microscopy, GC – MS, HPLC, NMR and FT-IR also help complement the findings of XRD

Explosives

Explosives are commonly recovered as powdered mixes, gels and liquids. Such materials are often recovered from hijack suspects or at post-blast sites. While it is simple to identify the pure material the analysis of residues collected from a blast site can prove to be a daunting task. It can contain a mix of both organic and inorganic material such as human blood, flesh, pellets, broken glass and residues of other damaged material. At times the concentration of explosive in the residue could be so low that analysis and detection can require separation and extraction prior to analysis.

Paints and pigments

Samples of paints and pigments are generally recovered as minute flakes from clothes of accident victims or vehicles involved in accidents. The collected specimens are compared for preliminary colour matching by optical studies followed by presence of crystalline components existing as pigments such as titanium dioxide, lead oxide or red lead. The more the number of crystalline components present the better is the degree of match. A final confirmation can be reached by ascertaining the organic composition by pyrolysis GC analysis.

Textile fibers

It is common to recover pieces of cloth as evidence from scene of some crimes. Textile fibers are a composite of crystalline and amorphous molecules. The extent of similarity between the recovered material and accused person’s clothing can be useful evidence. XRD helps establish the crystallinity of such textile specimens. Textiles such as cotton, polyester and nylon show significant crystallinity whereas wool fibers are predominantly amorphous.

X-ray diffraction is a useful tool in the hands of the forensic analyst as it serves to complement the findings of other analytical techniques. In recent years the technique has also found widespread application in the rapid screening of passenger baggage at major airports across the world. Specially designed screening systems help screen passenger baggage for explosives and narcotics without the need for sniffer dogs or manual searches. Such systems offer significant assistance in prevention of drug smuggling and acts of terrorism without deputing additional manpower or inconveniencing other passengers.

X-ray diffraction or XRD has made valuable contributions in the field of geology and mining. Geology is the scientific study on structure of planet earth, formation of rocks, sediments and minerals. Mining is an applied science which concerns with extraction of ores, fossil fuels for energy needs and minerals for commercial processing.

Minerals are inorganic materials majority of which exhibit a degree of crystallinity. Each mineral generates its unique x-ray diffraction pattern which serves to identify it. The diffraction pattern can be matched with a library of over 17,000 patterns for different minerals offered by the International Centre for Diffraction Data (ICDD).Using the data base helps in both qualitative and quantitative estimation of minerals. In addition x-ray diffraction provides details on degree of crystallinity, amorphous content, grain size, lattice deformations due to strain and can help trace the origins of minerals.

XRD Analysis complements information obtained from other analytical techniques such as polarized light microscopy and scanning electron microscopy. However, the lower cost of XRD makes it the preferred choice for studies directed towards evaluation of fine grain minerals and mixtures or intergrowths at the microscopic level. However, for elemental composition and texture analysis one has to resort to scanning probe microscopy and scanning electron microscopy.

Minerals exist in the Earth’s crust under different forms such as rocks, clays and sediments or as nodules on the sea bed. Some typical practices for sampling of geological specimens are outlined in the article.

Rocks

Rocks can vary in size as well as in uniformity of composition. The surface composition can differ from the interior due to weathering under natural environmental surroundings. Sampling plays a crucial role in rock analysis. The sample size should be at least 5 – 10 g. It should comprise of different layer cuttings or drillings at different surface points which after fine grinding in a pulverising mill is dried at around 60°C overnight and quartered to get a uniform sample.The sample thus obtained is mounted onto a surface mount to obtain a uniform surface for analysis.

Clays

Like rocks 10- 15 g of clay sample is taken and any rock bits are sieved out. The fine clay mix is ground in a mortar and pestle to obtain stone free specimen. The powder is transferred to a centrifuge tube topped up with Calgon solution and after shaking is centrifuged to remove the course sediments. Centrifugation is repeated to permit sedimentation of fine solids. A small portion of the clear sediment is spread on a glass slide and allowed to dry. The slide is then mounted onto the sample stage of goniometer and subjected to the typical XRD analysis. In addition to mineralogical analysis it also gives useful information on particle size.

Weathering of Rocks and minerals

The composition of minerals undergoes continual changes due to environmental factors such as acid mine drainage, hydrological changes, changes in temperature and pressure due to rock dynamics. Such changes can be monitored using XRD analysis and can help establish the evolution of mineral resources in different mineral rich areas. The data collected from remote sensing can be correlated with the XRD analysis data to reach commercial decisions concerning mining activities.

Gem and Jewellery

XRD is a useful tool for grading of minerals in terms of their origin, degree of crystallinity and purity. Such details are essential for jewellery makers to manufacture items with features in demand in the consumer market.

Cosmetics have been in use since time immemorial. In earlier ages several potentially toxic inorganic pigments such as malachite, mercuric sulphide or white lead were used in cosmetic preparations. In contemporary products several organic components such as parabens, alkylphenols, etc have also been included. It was a common concept that cosmetic products were only meant for external applications and therefore were safe as skin was believed to be impermeable to external applications. However, it is now established that skin is not an impermeable barrier which can prevent penetration of chemical compounds present in cosmetics. A common user is primarily concerned with irritations and allergies only due to use of such products but it has been established that systematic absorption can cause chronic toxicity resulting in harmful consequences.

It is also a common belief that cosmetic products are safe as the cosmetics industry is under regulation of US Food and Drug Administration. On the contrary this is a self regulated industry. Undoubtedly there are several established global brands which exercise strict quality control during manufacturing but it is also true that in the grey markets, especially in third world countries, counterfeit products find a flourishing market. Such fake products are not manufactured under any controls worth mentioning and their use can do more harm than good.

Cosmetics come in various forms such as lipsticks, soaps, toothpastes, body deodorants, face powders, nail polishes, shaving creams, face creams and anti- ageing creams, sunshades, moisturizers, shampoos, hair oils, etc. The list is virtually endless and new products are continuously being added to keep pace with growing consumer demands. The formulations are available as powders, creams, gels, lotions and liquid suspensions containing un- dissolved solids. Several techniques find use in analysis of cosmetic products some of which are Transmission Electron Microscopy, Atomic Force Microscopy, X-Ray Fluorescence, Laser Desorption Ionization Mass Spectroscopy, Inductively Coupled Optical Emission Spectroscopy and X Ray Diffraction analysis. Most of the mentioned techniques involve high initial investments so become unaffordable by common testing laboratories. Out of these XRD is affordable and does provide valuable information on components which exhibit crystalline or semi-crystalline properties. However, the role of expensive instruments cannot be underplayed and should be restored to when specific details on sample constituents are required.

X-ray diffraction reveals the proportion of crystalline and amorphous content of a product. Sharp peaks result from the crystalline content and amorphous content results in broad humps. The identity of crystalline compound and can be established through a match with the data base of known crystalline materials.

XRD is a non- destructive technique which also does not require sample pretreatment or dilutions. It makes use of a collimated beam of x-rays that is directed onto the sample holder,tube or a powder smeared evenly on a glass slide. The diffraction pattern results from constructive interference of beams scattered by the faces of crystal planes of the sample. The x-ray incident beam scans the sample over a range of degrees by rotating the sample stage at a predetermined angular scan rate

Nanotechnology has brought about a revolution in fields of materials science, electronics, pharmaceuticals, foods, etc. Cosmetics have not been left out and nano particles (having diameters below 100nm) are being increasingly used to improve the desirable features of cosmetic products. Nano emulsion in the form of lotions and conditioners are commonly available. Studies are reported on nano emulsions used in sunscreens comprising of TiO2 nano particles. Similarly silver nano particles find use in some soaps, toothpastes and face creams and act as bactericides. Similarly other nano particles have shown promise in other commonly used cosmetic products.

X-ray diffractionhas played a significant role in studies on such particles as their properties achieve the desirable cosmetic features and also their uptake by the skin.

Pharmaceutical formulations are available as tablets, capsules, ointments, pills, oral liquids, aerosol sprays, etc. Even a single drug can be found in several different formulations which impart it different characteristics as per administration requirements .In case of solid formulations X-ray diffraction has been used as a non-destructive technique for testing of inconsistencies in manufactured batches, […]

Forensic analysis is a scientific study which assists criminal investigations. Whenever any crime takes place there is exchange of material between the accused and the victim such as textile fibers, blood stains, gunshot residues, broken glass, saliva, semen, etc. Chemical and biological tests on such materials can provide undisputed evidence to nail down the suspect. […]

X-ray diffraction or XRD has made valuable contributions in the field of geology and mining. Geology is the scientific study on structure of planet earth, formation of rocks, sediments and minerals. Mining is an applied science which concerns with extraction of ores, fossil fuels for energy needs and minerals for commercial processing. Minerals are inorganic […]

Cosmetics have been in use since time immemorial. In earlier ages several potentially toxic inorganic pigments such as malachite, mercuric sulphide or white lead were used in cosmetic preparations. In contemporary products several organic components such as parabens, alkylphenols, etc have also been included. It was a common concept that cosmetic products were only meant […]

The growth of our civilization has seen a parallel growth in the food industry. In pre-historic ages humanity was dependent mainly on vegetables, fruits and meat for its daily food intake. However, over the years there has been an increasing demand for processed synthetic foods to cater to the needs of a growing population and […]